CodeMod: google::SetCommandLineOption to gflags::SetCommandLineOption
CodeMod: google::SetCommandLineOption to gflags::SetCommandLineOption

Summary:
CodeMod: `google::SetCommandLineOption` to `gflags::SetCommandLineOption`.

For gflags, `namespace google` is deprecated in favor of `namespace gflags`.

Automated with:

```lang=bash
hg grep -lw google::SetCommandLineOption | xargs perl -pi -e 's,\bgoogle(::SetCommandLineOption)\b,gflags\1,g'
```

Reviewed By: igorsugak, jsedgwick

Differential Revision: D4665863

fbshipit-source-id: 87c22b278370b41011e4da20e2d8e8d557ff187b

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